Decouple the session validators from im-online (#7127)

* Decouple the session validators from im-online

* .

* Add SessionInterface trait in im-online

Add ValidatorId in im-online Trait

Make im-online compile

Make substrate binary compile

* Fix merging issue

* Make all compile

* Fix tests

* Avoid using frame dep in primitives via pallet-session-common

* Merge ValidatorSet into SessionInterface trait

Wrap a few too long lines

Add some docs

* Move pallet-sesion-common into pallet-session

* Move SessionInterface to sp-session and impl it in session pallet

Ref https://github.com/paritytech/substrate/pull/7127#discussion_r494892472

* Split put historical::FullValidatorIdentification trait

* Fix line width

* Fix staking mock

* Fix session doc test

* Simplify <T as ValidatorIdentification<AccountId>>::ValidatorId as ValidatorId<T>

* Nits

* Clean up.

* Make it compile by commenting out report_offence_im_online bench

* Tests

* Nits

* Move OneSessionHandler to sp-session

* Fix tests

* Add some docs

* .

* Fix typo

* Rename to ValidatorSet::session_index()

* Add some more docs

* .

* Remove extra empty line

* Fix line width check

.

* Apply suggestions from code review

* Cleaup Cargo.toml

* Aura has migrated to Pallet now

Co-authored-by: Tomasz Drwięga <tomasz@parity.io>

substrate/frame/offences/benchmarking/src/lib.rs

@@ -26,7 +26,7 @@ use sp_std::vec;
 
 use frame_system::{RawOrigin, Module as System, Config as SystemConfig};
 use frame_benchmarking::{benchmarks, account};
-use frame_support::traits::{Currency, OnInitialize};
+use frame_support::traits::{Currency, OnInitialize, ValidatorSet, ValidatorSetWithIdentification};
 
 use sp_runtime::{Perbill, traits::{Convert, StaticLookup, Saturating, UniqueSaturatedInto}};
 use sp_staking::offence::{ReportOffence, Offence, OffenceDetails};
@@ -176,6 +176,34 @@ fn make_offenders<T: Config>(num_offenders: u32, num_nominators: u32) -> Result<
 	Ok((id_tuples, offenders))
 }
 
+fn make_offenders_im_online<T: Config>(num_offenders: u32, num_nominators: u32) -> Result<
+	(Vec<pallet_im_online::IdentificationTuple<T>>, Vec<Offender<T>>),
+	&'static str
+> {
+	Staking::<T>::new_session(0);
+
+	let mut offenders = vec![];
+	for i in 0 .. num_offenders {
+		let offender = create_offender::<T>(i + 1, num_nominators)?;
+		offenders.push(offender);
+	}
+
+	Staking::<T>::start_session(0);
+
+	let id_tuples = offenders.iter()
+		.map(|offender| <
+				<T as ImOnlineConfig>::ValidatorSet as ValidatorSet<T::AccountId>
+			>::ValidatorIdOf::convert(offender.controller.clone())
+			.expect("failed to get validator id from account id"))
+		.map(|validator_id| <
+				<T as ImOnlineConfig>::ValidatorSet as ValidatorSetWithIdentification<T::AccountId>
+			>::IdentificationOf::convert(validator_id.clone())
+			.map(|full_id| (validator_id, full_id))
+			.expect("failed to convert validator id to full identification"))
+		.collect::<Vec<pallet_im_online::IdentificationTuple<T>>>();
+	Ok((id_tuples, offenders))
+}
+
 #[cfg(test)]
 fn check_events<T: Config, I: Iterator<Item = <T as SystemConfig>::Event>>(expected: I) {
 	let events = System::<T>::events() .into_iter()
@@ -220,7 +248,7 @@ benchmarks! {
 		// make sure reporters actually get rewarded
 		Staking::<T>::set_slash_reward_fraction(Perbill::one());
 
-		let (offenders, raw_offenders) = make_offenders::<T>(o, n)?;
+		let (offenders, raw_offenders) = make_offenders_im_online::<T>(o, n)?;
 		let keys =  ImOnline::<T>::keys();
 		let validator_set_count = keys.len() as u32;
 

substrate/frame/offences/benchmarking/src/mock.rs

@@ -29,7 +29,7 @@ use sp_runtime::{
 	traits::IdentityLookup,
 	testing::{Header, UintAuthorityId},
 };
-
+use pallet_session::historical as pallet_session_historical;
 
 type AccountId = u64;
 type AccountIndex = u32;
@@ -130,6 +130,7 @@ impl pallet_session::Config for Test {
 	type DisabledValidatorsThreshold = ();
 	type WeightInfo = ();
 }
+
 pallet_staking_reward_curve::build! {
 	const I_NPOS: sp_runtime::curve::PiecewiseLinear<'static> = curve!(
 		min_inflation: 0_025_000,
@@ -175,6 +176,7 @@ impl pallet_staking::Config for Test {
 impl pallet_im_online::Config for Test {
 	type AuthorityId = UintAuthorityId;
 	type Event = Event;
+	type ValidatorSet = Historical;
 	type SessionDuration = Period;
 	type ReportUnresponsiveness = Offences;
 	type UnsignedPriority = ();
@@ -214,6 +216,7 @@ frame_support::construct_runtime!(
 		Session: pallet_session::{Module, Call, Storage, Event, Config<T>},
 		ImOnline: pallet_im_online::{Module, Call, Storage, Event<T>, ValidateUnsigned, Config<T>},
 		Offences: pallet_offences::{Module, Call, Storage, Event},
+		Historical: pallet_session_historical::{Module},
 	}
 );